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https://issues.apache.org/jira/browse/AIRAVATA-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16676989#comment-16676989
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Marcus Christie commented on AIRAVATA-2872:
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I believe I've fixed all places in the JPA mappings that might cause OpenJPA to
null out of a foreign key reference because the mapped entity is not in the
data model. As a guard against this happening accidentally, I've also added the
NOT NULL constraint to all foreign key columns in the schema.
> registry-refactoring: OpenJPA doesn't persist setting a field to null
> ---------------------------------------------------------------------
>
> Key: AIRAVATA-2872
> URL: https://issues.apache.org/jira/browse/AIRAVATA-2872
> Project: Airavata
> Issue Type: Bug
> Components: Registry API
> Reporter: Marcus Christie
> Assignee: Marcus Christie
> Priority: Major
>
> In OpenJPA, the default handling of null values on detached instances is to
> treat them as "unloaded" when merging them, meaning it treats them as if they
> are simply missing instead of treating them as having been set to null. That
> is, it skips over null value and doesn't update the corresponding fields on
> the persistent instances to have a null value.
> See https://stackoverflow.com/a/2569417/1419499
> See also official docs:
> http://openjpa.apache.org/builds/2.4.3/apache-openjpa/docs/ref_guide_remote.html#ref_guide_detach,
> however it's hard to understand how to make use of this in our context.
> See also this discussion
> http://openjpa.208410.n2.nabble.com/null-values-not-updating-td3224059.html
> I traced the OpenJPA code to these lines in VersionAttachStrategy:
> {code:java}
> int detach = (isNew) ? DETACH_ALL : broker.getDetachState();
> FetchConfiguration fetch = broker.getFetchConfiguration();
> try {
> FieldMetaData[] fmds = sm.getMetaData().getFields();
> for (int i = 0; i < fmds.length; i++) {
> switch (detach) {
> case DETACH_ALL:
> attachField(manager, toAttach, sm, fmds[i], true);
> break;
> case DETACH_FETCH_GROUPS:
> if (fetch.requiresFetch(fmds[i])
> != FetchConfiguration.FETCH_NONE)
> attachField(manager, toAttach, sm, fmds[i], true);
> break;
> case DETACH_LOADED:
> attachField(manager, toAttach, sm, fmds[i], false);
> break;
> }
> }
> } finally {
> {code}
> The detach state is {{DETACH_LOADED}} which causes OpenJPA to treat nulls as
> unloaded and thus it skips merging those values in.
> I think with a configuration change we can get this to work, but it's not
> obvious what all the flags mean, so this will take some research.
> One other question I have, is how did this work before. It would be worth
> checking to see how the old registry code had configured OpenJPA.
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